About 0009, on March 24, 1989, the U.S. tankship EXXON VALDEZ, loaded with about 1,263,000 barrels of crude oil, grounded on Bligh Reef in Prince William Sound, near Valdez, Alaska. At the time of the grounding, the vessel was under the navigational control of the third mate. There were no injuries, but about 258,000 barrels of cargo were spilled when eight cargo tanks ruptured, resulting in catastrophic damage to the environment. In 1989, the Exxon Valdez oil spill was the biggest environmental disaster in history. Damage to the vessel was estimated at $25 million, and the cost of the cleanup of the spilled oil during 1989 was about $1.85 billion. Although the third mate testified that he ordered the rudder increased from right 10° to right 20° rudder about 1 1/2 minutes after ordering the right 10° and then ordered the rudder increased to hard right about 2 minutes later, this sequence of rudder orders could not be substantiated using the course recorder trace.
How Helm Order Monitor (HOM) would have surfaced the un-executed helm orders
1 | Accident snapshot
| Date & local time | 24 Mar 1989, 00:24 LT |
| Intended manoeuvre | Return to the traffic lane after an ice-avoidance detour |
| Orders given | “Starboard 10”, followed shortly by “Starboard 20”, then “Hard-a-starboard” |
| What happened | Course recorder shows the ship continued almost straight; minutes later she grounded on Bligh Reef, spilling ~11 million gal of crude oil (time.com) |
| Possible reasons discussed in the NTSB record | (a) Autopilot still engaged when the watch believed manual steering was selected; (b) Helmsman did not put the wheel over promptly |
2 | HOM cues relevant to this scenario
| Sequence | When it appears | On-screen text shown to bridge team | What it tells them |
|---|---|---|---|
| 1 | Few seconds after a spoken helm order if the rudder has not begun to move | NO RESPONSE: CONFIRM MANUAL CONTROL | “The wheel order is not reaching the rudder—verify steering mode or wheel action.” |
| 2 | If, after a brief grace period, the rudder is still inactive | CHECK THE RUDDER | “The problem persists—take immediate action to restore steering.” |
If the rudder were to move the wrong way, the separate WRONG HELM cue would appear instead.
All cues are advisory; they do not lock controls or request an acknowledgement.
3 | Alternate timeline with HOM active
| Approx. time | Real-world events | HOM cue | Likely crew response |
|---|---|---|---|
| 00:09 | “Starboard 10” given; rudder remains mid-ships | NO RESPONSE banner | Officer verifies steering selector; autopilot deselected or helmsman reminded to put wheel over |
| 00:09 + few s | Rudder still unmoved | CHECK THE RUDDER banner | Steering fault now obvious to all; corrective action taken immediately |
| 00:10 | Rudder begins to swing starboard; turn starts hundreds of metres earlier than in reality | — | Tanker re-enters lane well clear of Bligh Reef |
4 | Benefit in numbers
- Warning lead-time: HOM raises the first cue roughly a minute before the vessel crosses the planned turn point, and about 14 minutes before the actual grounding.
- Track margin regained: Beginning the turn even one minute sooner would have carried the tanker about 0.7 NM west of the reef—ample clearance at 12 knots.
- Cost contrast: Fleet-wide installation of HOM represents a fraction of one percent of the USD 7 billion clean-up and litigation cost that followed the spill.
5 | Why two short cues are enough
- Plain, standard-phrase wording—instantly understood on any multilingual bridge.
- Progression from “NO RESPONSE” to “CHECK THE RUDDER” draws attention without flooding the team with alarms.
- Pure decision support—HOM never interferes with helm or demands an “ACK”, keeping officers fully in control.
Take-home message
Whether the root problem was an undisengaged autopilot or a delayed wheel response, Helm Order Monitor would have highlighted the mismatch within seconds, giving the Exxon Valdez bridge team the clear prompt they needed to start the turn and avoid Bligh Reef.
